149 lines
5.5 KiB
C
149 lines
5.5 KiB
C
/* $NetBSD: uvm_anon.h,v 1.7 1998/03/09 00:58:56 mrg Exp $ */
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/*
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* XXXCDC: "ROUGH DRAFT" QUALITY UVM PRE-RELEASE FILE!
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* >>>USE AT YOUR OWN RISK, WORK IS NOT FINISHED<<<
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*/
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/*
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*
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* Copyright (c) 1997 Charles D. Cranor and Washington University.
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. All advertising materials mentioning features or use of this software
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* must display the following acknowledgement:
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* This product includes software developed by Charles D. Cranor and
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* Washington University.
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* 4. The name of the author may not be used to endorse or promote products
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* derived from this software without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
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* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
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* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
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* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
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* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
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* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*
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* from: Id: uvm_anon.h,v 1.1.2.4 1998/01/04 22:43:39 chuck Exp
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*/
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#ifndef _UVM_UVM_ANON_H_
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#define _UVM_UVM_ANON_H_
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/*
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* uvm_anon.h
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*/
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/*
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* anonymous memory management
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*
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* anonymous virtual memory is short term virtual memory that goes away
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* when the processes referencing it go away. an anonymous page of
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* virtual memory is described by the following data structure:
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*/
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struct vm_anon {
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int an_ref; /* reference count [an_lock] */
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simple_lock_data_t an_lock; /* lock for an_ref */
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union {
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struct vm_anon *an_nxt; /* if on free list [afreelock] */
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struct vm_page *an_page;/* if in RAM [pageqlock] */
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} u;
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int an_swslot; /* drum swap slot # (if != 0) [pageqlock] */
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};
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/*
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* a pool of vm_anon data structures is allocated and put on a global
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* free list at boot time. vm_anon's on the free list use "an_nxt" as
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* a pointer to the next item on the free list. for active vm_anon's
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* the data can be in one of the following state: [1] in a vm_page
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* with no backing store allocated yet, [2] in a vm_page with backing
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* store allocated, or [3] paged out to backing store (no vm_page).
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*
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* for pageout in case [2]: if the page has been modified then we must
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* flush it out to backing store, otherwise we can just dump the
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* vm_page.
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*/
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/*
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* anonymous virtual memory pages (vm_anon's) live in anonymous memory
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* maps. anonymous memory maps can be shared between processes.
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* different subsets of an anonymous memory map can be referenced by
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* processes (see below). an anonymous map is described by the following
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* data structure:
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*/
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#define VM_AMAP_PPREF /* use a per-page reference count for split
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vm_map_entry_t's. */
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struct vm_amap {
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simple_lock_data_t am_l; /* simple lock [locks all vm_amap fields] */
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int am_ref; /* reference count */
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int am_flags; /* flags */
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int am_maxslot; /* max # of slots allocated */
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int am_nslot; /* # of slots currently in map ( <= maxslot) */
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int am_nused; /* # of slots currently in use */
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int *am_slots; /* contig array of active slots */
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int *am_bckptr; /* back pointer array to am_slots */
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struct vm_anon **am_anon; /* array of anonymous pages */
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#ifdef VM_AMAP_PPREF
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int *am_ppref; /* per page reference count (if !NULL) */
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#endif
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};
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#define AMAP_SHARED 0x1 /* am_flags: shared amap */
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#define AMAP_REFALL 0x2 /* flag to amap_ref() */
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/*
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* note that am_slots, am_bckptr, and am_anon are arrays. this allows
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* fast lookup of pages based on their virual address at the expense of
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* some extra memory. [XXX: for memory starved systems provide alternate
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* functions?]
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*
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* 4 slot/page example, with slots 1 and 3 in use:
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* ("D/C" == don't care what the value is)
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*
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* 0 1 2 3
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* am_anon: NULL, anon0, NULL, anon1 (actual pointers to anons)
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* am_bckptr: D/C, 1, D/C, 0 (points to am_slots entry)
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*
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* am_slots: 3, 1, D/C, D/C (says slots 3 and 1 are in use)
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*
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* note that am_bckptr is D/C if the slot in am_anon is set to NULL.
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* to find the entry in am_slots for an anon, look at am_bckptr[slot],
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* thus the entry for slot 3 in am_slots[] is at am_slots[am_bckptr[3]].
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* in general, if am_anon[X] is non-NULL, then the following must be
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* true: am_slots[am_bckptr[X]] == X
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*
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* note that am_slots is always contig-packed.
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*/
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/*
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* processes reference anonymous virtual memory maps with an anonymous
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* reference structure:
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*/
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struct vm_aref {
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int ar_slotoff; /* slot offset into amap we start */
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struct vm_amap *ar_amap; /* pointer to amap */
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};
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/*
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* the offset field indicates which part of the amap we are referencing.
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* locked by vm_map lock.
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*/
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#endif /* _UVM_UVM_ANON_H_ */
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